Cutting bit



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CUTTING BIT Filed Oct. 25, 1939 fie 7 INVENTOR. flara MMormw A TTORNEY.

BY WW MUM Patented Oct. 8, 1940 UNITED STATES CUTTING BIT Harry M.- Morrow, Canton, Ohio, assignor to The Bowdil Company Application October 25, 1939, Serial No. 301,183

4 Claims.

My invention relates in general to cutting bits and more particularly to bits for cutting coal or other substances.

In the mining of coal or other substances, a

cleft is cut in the lower level of the vein by means of a cutter bar around which revolves a power driven endless chain carrying a plurality of staggeredly arranged cutting bits constituting the subject matter of this invention. The shelf formed by the cleft is subsequently broken off by means of explosives or other suitable methods. When cutting the cleft, in the interest of economy and the saving of power, it is highly desirable that the cutting bits be not only strong and durable but also efficient in operation and free from drag.

An object of my invention is the provision of a cutting bit which requires a minimum amount of power to operate.

Another object of my invention is the provision of a cutting bit which produces very little drag.

Another object of my invention is the provision of a cutting bit which has a greater cutting clearance as the bit wears away.

Another object of my invention is to make the cutting clearance of the bit increase in substantial proportion to the amount that the cutting points of the bit wear away.

Another object of my invention is to make my bit have relatively narrow cutting faces for a substantial distance to give longer wear.

Another object of my invention is the provision of a cutting bit which is durable and adapted to cut through hard substances.

Another object of my invention is the provision of asolid double-ended rhomboidal and substantially diamond shaped bit having substantially diamond shaped cutting faces with concaved edges ofi-set in substantially parallel relation to each other to form cutting points at the diametrically opposed sharper angles of the rhomboid.

Another object of my invention is the provision of a solid double-ended rhomboidal and substantially diamond shaped bit having substantially diamond shaped faces with concave edges offset in substantially parallel relation to each other for substantially one-half the length of the longer dimension of the substantially diamond shaped faces to form cutting points at the diametrically opposed sharper angle of the rhomboid.

A still further object of my invention is the provision of a solid double-ended rhomboidal and substantially diamond shaped bit having a greater cutting clearance as the cutting points wear away.

Another object of my invention is the provision of a solid double-ended rhomboidal and substantially diamond shaped cutting bit having a relatively wide central body portion and relatively narrow edge portions and having concaved side walls between the relatively wide central portion and the relatively narrow edge portions.

Other objects and a fuller understanding of my-invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 shows a side elevationalview of my new and improved cutting bit;

Figure 2 shows a cross-sectional view of the bit taken along the line 22 of Figure l; t

Figure 3 shows a cross-sectional view of the bit taken along the line 3-3 of Figure 1;

Figure 4 shows a cross-sectional view of the bit taken along the line dof Figure 1;

Figure 5 shows a front elevational view of my improved cutting bit as shown in Figure 1;

Figure 6 shows a side elevational view of a modifiedform of my cutting bit;

Figure 7 shows a cross-sectional view of the modified bit taken along the line 'l-l' of Figure 6;

Figure 8 shows a cross-sectional View of the modified bit taken along the line 13-43 of Figure 6;

Figure 9 shows a cross-sectional view of the modified bit taken along the line 99 of Figure 6, and

Figure 10 shows the front elevational view of the modified bit as shown in Figure 6.

This invention constitutes an improvement over the rhomboidal shown in Patent No. 1,677,950, issued to N. K. Bowman on July 24, 1928 and assigned to the assignee of the present application. With reference to Figures 1 to 5, inclusive, my improved cutting bit is solid and may be made of hardened steel in order to withstand the severe cutting operations to which it is subjected. In side elevation, the body of the bit is substantially rhomboidal and in front elevation its cutting faces 20 and 2! are substantially diamond shaped and have concaved edges. The two, cutting faces 20 and 2| are substantially parallel and are offset relative to each other at a rhomboidal angle to form cutting points 22' and 23 at the diametrically opposed sharper angles of the rhomboid. The bits are removably mounted in the lugs of the endless power driven chain which revolves around the cutter bar. When one of the cutting points of the bits wears away the bits are reversed, giving a double cutting life to the bits. The bits are held in the chain lugs at a slight forward angle as shown in Figure 1. The central body portion 24 of a cutting bit is relatively wide and the rhomboidal edge portions wand 26 are relatively narrow, and the rhomboidal side walls 27, 28 and 29, 39 between the central body portion 24 and the edge portions 25 and 25 are concave to produce a greater cutting clearance as the cutting points 22 and 23 wear away.. The cutting faces 20 and 2| are identical and may diamond shaped cutting bit be considered as being defined by two substantially isosceles triangles having concaved sides and a common based area in the central body portion 24 of the bit. The angle at which the two cutting faces 20 and 2| is off-set may be referred to as the rhomboidal angle and may be defined, as shown by the dash-dot line 3| of Figure 1, as the angle included between a plane substantially parallel to said faces and a plane passing through the area of the common bases of the triangles and the juncture of the meeting concave sides 21, 28 and 29, 30 of the bit. I'he value of the rhomboidal angle and the distance between the cutting faces is such that a plane passing substantially perpendicular to either of said cutting faces and through the apex of the triangle coinciding with the broader angle of the rhomboid intersects the opposite face at a depth substantially one-half of the length thereof. The rhomboidal lateral concave sides 21, 28 and 29, 30 of the bit upon opposite sides of the plane passing upon the area of the common bases of the triangles converge arcuately in opposite directions in a plane passing substantially perpendicular tothe faces to provide a greater cutting clearance for the cutting faces in substantial proportion to the amount that the cutting points 22 and 23 wear away. The provision of the varying cutting clearance is progressively shown in Figures 2, 3 and 4. In the region near the cutting points shown by Figure 2, the clearance is rather small. At the cutting points of the bit, the

drag does not have an opportunity to manifest itself since the horizontal distance of the side walls across the bit in the rear of the cutting faces is small, and for this reason the cutting clearance in the region of the cutting points may be rather small without producing any substantial increase in the drag of the bits in the cutting operation. By making .only a very small clearance in the region of the cutting points, the cross-sectional area of the cutting points may be kept at a maximum, thereby giving additional strength to the cutting points which are subjected to a great deal of strain during the cutting operation. As the cutting points wear away, the horizontal distance of the side walls of the bit in rear of the cutting face increases, and for this reason an additional side wall drag would tend to be produced. In order to reduce this drag of the side walls because of the additional cutting side wall depth of the bit, I provide for making theside walls 21, 28 and 29, 30 of the bit arcuate or concaved, so that a greater clearance is produced as the cutting points of the bitswear away. The cutting clearance is indicated by the reference character 32 and the increase in cutting clearance is illustrated by the increased lateral space upon opposite sides of the cross-sectional views of Figures 3 and 4 over Figure 1, taken at different horizontal cutting sections through the bits. Therefore, with my improved cutting bit the drag is kept at a low minimum, regardless of the amount of wear that might occur upon the bits. Another result growing out of the concaved side walls 21, 28 and 29, 30 of my cutting bit is the fact that the cutting faces remain relatively narrow for a considerable distance and do not begin to broaden until the side walls approach the central body portion 24 of the bit. Because of this added narrow length, v

my improved bit gives substantially 50% more wear than the bit shown in Patent No. 1,677,950, and moreover the clearance is proportionately distributed throughout the entire life of the bit, so that the dragis always maintained at a low minimum value. is so constructed that there is a heavy supporting section behind the cutting surfaces of the bit. I In Figures 6 to 10, inclusive, I show a modified arrangement of my improved bit in that the concaved lateral rhomboidal sides of the bit meet at substantially a sharp juncture 33 in the central body portion of the bit. In this latter type, the cutting faces remain relatively narrower for a greater depth toward the central body portion 24 of the bit which gives even still morewear since there is more metal to wear away before the bit becomes too broad. The bits as shown in these views are substantially life-size and are drawn to scale, and the results produced offer a material advantage over the bits of the prior art.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to Without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. A double-ended bit comprising a solid piece of metal having rhomboidal side walls and substantially parallel opposite end cutting faces, said cutting faces being oif-set relative to each other and forming cutting points at the diametrically opposed sharper angles of the rhomboid, said bit having a relatively wide central body portion and relatively narrowedge portions, the rhomboidal side walls between the central body portion and edge portions being concaveand producing a greater cutting clearance as the cutting points wear away.

2. A double-ended bit comprising a solid piece of metal having rhomboidal side walls and substantially parallel opposite end cutting faces, said cutting faces being off-set relative to each other for substantially one-half their length and form ing cutting points at the diametrically opposed sharper angles of the rhomboid, said bit having a relatively wide central body portion and rela tively narrow edge portions, the rhomboidal side walls between the central body portion and edge portions being concave and producing a greater cutting clearance as the cutting points wear away.

3. A solid bit formed from a bar of stock which is substantially diamond shape in cross-section having a substantially diamond shaped cutting face disposed at an angle different than 90 degrees to the longitudinal axis of the bar, the side faces of the bit being concaved so as to provide a cutting clearance as the bit'wears away.

4. A double ended solid bit formed from a bar of stock which is substantially diamond shape in cross-section having substantially diamond shaped parallel cutting faces disposed at an angle different than 90 degrees to the longitudinal axis of the bar, the side faces of the bit being concaved so as'to provide cutting clearances as the bit wears away.

HARRY M. MORROW.

Besides, the shape of the bit- 

